fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nm[0];
    let m = nm[1];
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut upper = 1usize << 60;
    let mut lower = 0usize;
    while upper > lower {
        let middle = (upper + lower + 1) / 2;
        let mut carry = 0usize;
        let mut flg = true;
        for &v in a.iter() {
            if middle <= v {
                carry += v - middle;
            } else {
                if carry + v < middle {
                    flg = false;
                    break;
                } else {
                    carry -= middle - v;
                }
            }
        }
        if !flg {
            upper = middle-1;
        } else {
            lower = middle;
        }
    }
    println!("{}", upper / m);
}